Conventionally, in a system for a fuel injection, in one operation cycle of a cylinder of an internal combustion engine, fuel supply is performed by multiple times of fuel injection (multi-stage injection) to a combustion chamber from a fuel injection device having a fuel injection valve electromagnetically driven.
In such a fuel injection device, a boost power supply is generally configured to include a boost circuit including an inductive element and a switching element, and a capacitor which stores the boosted electric power. When the fuel injection valve is energized from the boost power supply, power is supplied by discharge from the capacitor. Therefore, when power is energized from the boost power supply, the voltage drops due to the discharge of the capacitor.
After discharging the capacitor, the power is charged by the boost circuit and returns to a boosted prescribed voltage. However, when the multiple times of injection are performed in a relatively short time, the charge may not be in time for the second and subsequent injections.
In contrast, there is also known a fuel injection device that performs the maximum number of times of executable injection with respect to the requested number of times of injection even when the boosted voltage decreases (see, for example, PTL 1). PTL 1 discloses a configuration in which a boosted voltage obtained by boosting a battery voltage is monitored by an engine controller unit, and when the boosted voltage drops below a set normal voltage, a valve opening time Pi of the fuel injection valve is extended to ensure the drive current necessary for the operation of the fuel injection valve. Thus, a highly reliable fuel injection device is achieved.